A variety of circumstances and situations exist where it is necessary to transmit electrical signals from one environment to another environment, and the two environments must be hermetically sealed or isolated from one another. Although satisfactory electrical connectors have been developed for many of these situations, others remain particularly difficult. For example, one such situation involves high speed, high capacity digital computers, referred to hereinafter as supercomputers.
Supercomputers generate relatively high heat densities, for example, in the range of 275 watts per cubic inch. To cool the components of supercomputers, a high density dielectric liquid coolant is delivered under pressure to and circulated over the components of the supercomputers. Because supercomputer components are submerged in the high density coolant, seals to the external environment must be maintained to control coolant flow and to contain the coolant within the supercomputer.
Transmission of high frequency signals to and from supercomputers has sometimes been achieved by using very small gage twisted wire pairs or coaxial cables. Twisted wire pairs are suitable for supercomputer signal transmission because the paired configuration achieves a controlled impedance signal path.
Twisted wire pairs, like other cables used with supercomputers, must penetrate the supercomputer cabinet through a seal. However, the insulation which surrounds the conductors of twisted wire pairs will act like a conduit through which the coolant will flow. Consequently, if the insulation is allowed to penetrate the boundary between the two environments, it becomes difficult to create and maintain a seal between the pressurized, liquid-filled interior of the cabinet and the exterior ambient environment.
To address the problem of coolant leakage via the insulation of twisted wire pairs, the insulation is stripped for a short length, each stripped conductor is physically isolated from adjacent conductors, and the separated stripped conductors are mounted in potting compound in a connector housing. Once the potting compound cures into a solid mass, the housing is mounted to the supercomputer cabinet.
Unfortunately, the fragility of the small gage conductors results in significant breaking and shorting of conductors during the stripping and mounting process. In addition, the separation of the twisted wire pairs creates discontinuities in the path impedance where the conductors are separated. Usually the integrity of the connections cannot be tested until after manufacturing of the assembly is complete. Because of the permanency of the potting compound, repairs to the twisted wire pairs are not practical.
To compensate for the expected percentage of damaged or nonfunctional twisted wire pairs, spare conductors are stripped and mounted in the potting compound. Often twice as many connections are Installed in a housing as are needed, based on the expectation that up to one half the twisted wire pairs will not transmit signals satisfactorily. This multiplies both labor and material costs for what already is a very labor intensive and costly manufacturing process.
While the above techniques address problems of maintaining seals in a supercomputer, other problems have resulted from use of the above techniques. For example, the need to manually strip each conductor and manually install the stripped conductor in physical isolation from adjacent conductors limits the number of conductors which can be closely positioned in a connector housing. This limitation on density of the conductors is exacerbated by the fact that approximately half of the twisted wire pairs are expected to not function satisfactorily, in part because adjacent stripped conductors are susceptible to shorting. Moreover, even when twisted wire pairs mounted in potting compound are initially functional, they remain susceptible to breaking and shorting at the point of contact with the hardened potting compound when the wires are strained or repeatedly flexed.
Copending U.S. patent application Ser. No. 08/234,253, now U.S. Pat. No. 5,491,300, assigned to the assignee of the present invention discloses a penetrator and flexible circuit assembly which addresses problems described above associated with penetrating the wall of a supercomputer. The maximum data transmission rates possible with such penetrator and flexible circuit assemblies are the maximum transmission speeds of electrical signals through wire, which have certain physical limitations.
Even computers which are not hermetically sealed from the environment in which they operate suffer from signal transmission speed limitation. For example, signal transmission between computers, between nodes of a multi-node network, or between processors of a single system is typically significantly slower than the clock speed of individual processors. Peripheral devices and file servers of the latest computer systems are also effected by latency resulting from delays in signal propagation from the computer to the devices and file servers through conventional cables.
High speed interface amongst computers and devices in local area networks (LANs) and other applications has been achieved with higher speed optoelectronic devices connected via optic fiber or optic fiber bundle in a fiber optic network. However, transmitting signals to and from a computer with such fibers typically require penetration of the computer housing by the fibers, by fiber bundles, or by connectors mounted in the computer housing.
It is against this background that the significant improvements and advancements of the present invention have taken place.